The study, to appear in this month's journal Science, examined DNA samples from 835 dogs, 95 of which had short legs. They found that a “single evolutionary event” explained the short, curved legs that define the look of dachshunds and other diminutive breeds like corgies.
“Through follow-up DNA sequencing and computational analyses, the researchers determined the dogs' disproportionately short limbs can be traced to one mutational event in the canine genome - a DNA insertion - that occurred early in the evolution of domestic dogs,” a statement published by the NIH said.
The scientists believe the “unexpected discovery” could help understand a form of human dwarfism.
"Every species, including canine and human, carries an amazing record of evolution scripted in its genome that can teach us about the mechanisms at work in biology, as well as about human health and disease," Eric Green, director of the National Human Genome Research Institute, said in the statement. "This work provides surprising evidence of a new way in which genome evolution may serve to generate diversity within a species."
They found that short-legged dogs have an extra copy of a gene for a growth-promoting protein that lacks a normal part of the DNA code called introns. Researchers concluded that this was a so-called retrogene that occurred after dogs evolved from wolves.
“These characteristics led researchers to conclude that the extra gene is a so-called retrogene that was inserted into the dog genome some time after the ancestor of modern dog breeds diverged from wolves.
The retrogene causes overproduction of a hormone that researches think may turn on growth receptors at the wrong time during gestation.
"Our findings suggest that retrogenes may play a larger role in evolution than has been previously thought, especially as a source of diversity within species," said the study's author, Heidi G. Parker. "We were surprised to find that just one retrogene inserted at one point during the evolution of a species could yield such a dramatic physical trait that has been conserved over time."